In known compacting machines used in earth moving operations and having a hydraulic travel motor, an operator controls the performance of the power train via the rotational speed of an internal combustion engine. To this end, a feed pump is coupled to the output shaft of the internal combustion engine, which produces a control pressure proportional to the rotational speed of the internal combustion engine. The control pressure acts on a pressure-dependent travel pump adapted to act on the travel motor. The output of the travel pump is proportional to the control pressure, so that the speed of travel is likewise proportional to the rotational speed of the internal combustion engine. The speed of travel is thus strictly governed by the rotational speed of the internal combustion engine.
EP 1722036 A2 discloses a method of controlling the performance of compacting machines used in earth moving operations and an appropriate device. In this case, hydraulic power control of the travel motor is achieved by an adjustable flow control valve present between the travel motor and a feed pump in the hydraulic main line. By means of this valve, the volumetric flow rate of the fluid supplied to the travel motor is varied quantitatively in proportion to a controlled variable derived from a measurement of the stiffness of the soil to be compacted.
DE 4425130 A1 and DE 112008002977 T5 reveal methods of controlling the drive independently of the rotational speed of the internal combustion engine.
In practice, the direction of travel or the acceleration of the vehicle concerned must be frequently changed under certain operating conditions, which leads to unfavorable fuel consumption and to a high degree of wear on the internal combustion engine.